The present invention relates to a chemical treatment apparatus and a chemical treatment method, and more particularly to a chemical treatment apparatus and a chemical treatment method which are applied to a cleaning treatment step and an etching step in a semiconductor device manufacturing process.
A wafer treatment using chemical has been hitherto performed in each process of a semiconductor device manufacturing field. For example, in a semiconductor wafer manufacturing process, such a wafer treatment is performed in a cleaning step for removing unneeded materials (contaminants) adhering to the surfaces of wafers, in a wet etching step of a process for forming semiconductor devices on wafers, etc. As the microstructure of semiconductor devices is finer, not only the cleaning effect, but also uniformity of wet etching are required to be more remarkably enhanced.
A dip treatment in which plural wafers to be treated (hereinafter referred to as "target wafer") are dipped into chemical all together is known as a typical chemical treatment method.
FIGS. 1A to 1C are diagrams showing a conventional chemical treatment apparatus using the dip treatment method. A chemical treatment apparatus 30 includes a nozzle type circulating treatment tank 31. As shown in FIG. 1A, chemical 40 is overflowed in the direction indicated by an arrow A from the treatment tank 31 into an outer tank 32 which is provided at the outer periphery of the treatment tank 31, and contaminant materials in the chemical 40 are discharged into the outer tank 32 together with the chemical 40. Thereafter, the chemical 40 in the outer tank 32 is guided through a pump 33 to a filter 34 in which the chemical 40 is filtered and cleaned, and then supplied into the treatment tank 31 again.
At this time, in order to effectively bring the chemical 40 into contact with the surface of a target wafer 50 dipped in the chemical 40 in the treatment tank 31, the chemical 40 is fed from the filter 34 to jet pipes 35 serving as nozzles which are provided at the bottom side in the treatment tank 31, and supplied into the treatment tank 31 through small jetting holes 36 formed on the jet pipes 35.
In the dip treatment, plural target wafers 50 are normally dipped in the chemical 40 while being arranged substantially in parallel and at predetermined intervals. Therefore, a pair of jet pipes 35 are disposed in the chemical treatment tank 30 so as to confront each other. The plural target wafers 50 are dipped between the jet pipes 35 and above the jet pipes 35 so that the arrangement direction of the target wafers 50 is substantially parallel to the length direction of the jet pipes 35. The jet holes 36 are formed in each jet pipe 35 so that the chemical 40 is jetted to the gaps between neighboring target wafers 50 and to the substantial centers of the target wafers 50 (in the directions indicated by arrows B of FIGS. 1A and 1B). These plural jet holes 36 are formed in each jet pipe 35 along the length direction of the jet pipe 35.
However, in the chemical treatment using the chemical treatment apparatus 30 shown in FIG. 1, all of the chemical 40 jetted from the jet pipes 35 does not necessarily flow upwardly and overflow from the treatment tank 31 into the outer tank 32, but a part of the chemical 40 convectively returns from the upper side of the target wafer 50 toward the jet pipes 35 as indicated by an arrow G in FIG. 1A. The chemical 40 which returns to the portions surrounding the jet pipes 35 contains various contaminant materials removed from the target wafer 50, and stagnates in the neighborhood of the bottom portion 31a of the treatment tank 31 as indicated by an arrow H in FIG. 1C, so that a dirty stagnant layer 41 is formed in the neighborhood of the bottom portion 31a. The chemical 40 stagnates in the neighborhood of the bottom portion 31a of the treatment tank 31 as described above because there is not provided any means of inducing flow of the chemical 40 in the neighborhood of the jet pipes 35, particularly in the neighborhood of the bottom portion 31a of the treatment layer 31 which is at the lower side of the jet pipes 35.
When the stagnant layer 41 as described above is formed, the circulating efficiency of the chemical 40 in the treatment tank 31 is lowered. As a result, for example when the chemical treatment is a water washing treatment after the wet etching step, a large amount of wet etching agent to be removed remains ununiformly on the surface of the target wafer 50, and thus the uniformity of the etching in the plane of the target wafer 50 is deteriorated. Further, the lowering of the circulating efficiency of the chemical 40 reduces the washing effect of the target wafer 50, and the contaminant materials taken into the chemical 40 also adhere to the surface of the target wafer 50 again. if semiconductor devices are manufactured while the target wafers 50 are left contaminated, the electrical reliability and the manufacturing yield of the semiconductor devices are reduced.
Further, in order to remove the stagnant layer 41, the treatment tank 31 must frequently washed, and the chemical 40 being used must be more frequently exchanged. Therefore, the following various troubles occur: a large amount of labor is imposed on a maintenance work; the manufacturing cost rises; the manufacturing yield is reduced because the workability of the chemical treatment apparatus 30 is reduced, etc.